1) Field of the Invention
This invention relates to the formation of structural members and, more particularly, relates to cutter wheels for machining structural members.
2) Description of Related Art
Cutter wheels are well known for machining structural members to specific configurations. A cutter wheel is generally a disk-shaped wheel with blades that extend in an outwardly radial direction. The blades may be formed as a unitary part of the disk-shaped wheel or may be removable inserts that are secured within spaces in the wheel by set screws or other attachment devices. The wheel is typically formed of steel, and, if removable blade inserts are used, the blade inserts can be formed of a variety of materials such as high speed steel or carbide. A shaft connects the cutter wheel to a rotational device such as an electric motor so that the cutter wheel is rotated about a central rotational axis. In operation, the rotating cutter wheel is brought into contact with a workpiece so that the blades remove material from the workpiece to achieve the desired shape of the structural member.
Because of the configuration of the cutter wheel and rotational device, some complex structural members are difficult to form. An example of such a complex structural member 50 is shown in FIG. 5. The structural member 50 includes T-shaped stiffeners 54 (“T-stiffeners”) that extend from a base portion 52. Webs 58 of the T-stiffeners 54 extend perpendicular to the base portion 52, and flanges 60 of the T-stiffeners 54 extend parallel to the base portion 52 from ends of the webs 58 distal to the base portion 52. The flanges 60 of adjacent T-stiffeners 54 are located so closely to one another that the rotational device 70 cannot be positioned between the T-stiffeners 54. It is possible, however, to position the rotational device 70 opposite the flanges 60 from the base portion 52 such that a shaft 140 extends from the rotational device 70 to a cutter wheel 100 between the T-stiffeners 54, as shown in FIG. 5. The rotational axis of the cutter wheel 100 is typically perpendicular to the base portion 52 of the structural member 50.
In this orientation, inadvertent contact can occur between the cutter wheel 100 and the structural member 50. For example, when machining the base portion 52 of the structural member 50, the central disk-shaped portion 112 of the cutter wheel 100 is pressed against the base portion 52 and translated along the length of the base portion 52. The central portion 112 rubs against the base portion 52, and this rubbing can generate significant frictional heat that can deform, mar, or otherwise damage the surface of the base portion 52 and the cutter wheel 100. Further, material parts can become caught between the central portion 112 of the cutter wheel 100 and the base portion 52. The material parts can scratch the base portion 52 and, in some cases, the frictional heat can cause the material parts to be welded to the structural member 50 resulting in unwanted build-up on the structural member 50. Cooling fluid can be used to reduce the friction between the cutter wheel 100 and the structural member 50, but the cooling fluid is prevented from flowing between the cutter wheel 50 and the base portion 52, for example, when the central portion 112 is pressed against the base portion 52.
Further, the geometry of some structural members prevents their formation using a conventional cutter wheel. For example, the structural member 50a shown in FIG. 6 includes a curved base portion 52a with T-stiffeners 54a extending therefrom. A cutter wheel 100 can be positioned between the T-stiffeners 54a by extending the shaft 140 between the T-stiffeners 54a as described above, but the rubbing problems described above are more severe due to the curvature of the base portion 52a. Further, in order to follow the curvature of the base portion 52a, the cutter wheel 100 must be rotated against the base portion 52a as the cutter wheel 100 is translated along the base portion 52a, but such rotation is prevented by the contact that results between the curved base portion 52a and the central portion 112 of the cutter wheel. Thus, a conventional cutter wheel 100 configured in that manner cannot properly machine all the sections of the structural member 50a. 
One proposed solution for forming such complex structural members is to mount the cutter wheel on a right-angle head. The right-angle head transmits the torque from the shaft to the cutter wheel and engages the shaft and the cutter wheel such that the cutter wheel rotates about an axis that is perpendicular to the axis of the shaft. Depending on the geometry of a particular structural member, some cutter wheels can be used with the right-angle head to machine complex structural members similar to the one shown in FIG. 6. The right-angle head, however, adds to the tooling cost for the machining process. Additionally, the use of the right-angle head can complicate the machining process. For example, if some of the machining of a structural member is done with the right-angle head and some is done without, the machining process must be stopped so that the right-angle head can be mounted or dismounted from the rotational device and the cutter wheel. Thus, the use of a right-angle head increases the time and cost of manufacture and the likelihood of errors during manufacture.
Alternatively, complex structural members of the type shown in FIGS. 5 and 6 can also be manufactured by forming the T-stiffeners separate from the base portion, machining the T-stiffeners and base portion to the required dimensions separately, and thereafter joining the T-stiffeners to the base portion. The base portion and the T-stiffeners individually can be machined using a conventional wheel cutter without the use of a right-angle head. However, joining the T-stiffeners to the base portion requires the use of a joining method such as welding, riveting, screwing, bolting, clipping, or the like. This adds a step to the manufacturing process, thereby increasing the time and cost of manufacture for the structural member. Additionally, the resulting joint may weaken and/or add weight to the structural member.
Thus, there exists a need for an improved cutter wheel that addresses the foregoing issues. Particularly, the cutter wheel should be capable of machining a variety of structural members including, but not limited to, structural members that have a curved base portion with webs and flanges extending therefrom. The cutter wheel advantageously should not require the use of a right-angle head or other special device for connecting the cutter wheel to the rotational device. Additionally, the cutter wheel should be capable of high speed machining to minimize the time required for machining the structural member without presenting a significant risk to nearby personnel or equipment.